MOC--The First Year--Top 10

Wind: Recent Sand Movement

Observations by the Mars Global Suveyor (MGS) Mars Orbiter Camera (MOC)
obtained in July, August, and September 1998, suggest that some of the
windblown dunes on Mars are active today, despite the planet's relatively
thin atmosphere. Martian air at the surface of the planet is about 100
times thinner than Earth's air at Sea Level.

Mars geologists have known since 1972 that Mars has big, low-albedo
(dark-toned) sand dune fields. One area of dunes, in particular, is
quite extensive and circles the north polar ice cap of the red planet.
The north polar dunes were not visible to MOC until late July 1998,
because the region had been in winter-time darkness between
mid-February and mid-July of 1998. When the Sun finally rose over the
north polar regions, MGS MOC saw that the dunes were coated with thin,
bright frost. In some places, however, the frost had been removed to
reveal the dark sand beneath. Some of these dark spots show streaks of
sand that was blown out over the surface of the frost-covered dunes.
Because the frost can only be as old as the most recent winter (which
ended mid-July), the streaks indicate that sand has been moving very
recently on the martian surface. Observation of sand movement can be
helpful in determining the rate of windblown sediment transport on
Mars--a key factor in assessing risk posed by sand and dust to future
landers, rovers, and human explorers.

The picture shown here--MOC image 50805--was taken on August 22, 1998.
The image has a resolution of about 2.5 meters (8 feet) per
pixel. The scene is 1.8 km (1.1 miles) by 1.1 km (0.7 mi) in size.
North is toward the upper right, illumination is from the lower left,
and the center is located at 76.96°N, 217.24°W.
(CLICK HERE for a context image).
The image was also the subject of an
earlier MGS MOC release on October 31, 1998.

Note: This MOC image is made available
in order to share with the public the excitement of new
discoveries being made via the Mars Global Surveyor spacecraft.
The image may be reproduced only if the
image is credited to "Malin Space Science Systems/NASA".
Release of this image does not constitute a release of
scientific data. The image and its caption should not be
referenced in the scientific literature. Full data releases
to the scientific community are scheduled by the Mars Global
Surveyor Project and NASA Planetary Data System. Typically, data
will be released after a 6 month calibration and validation period.

Malin Space Science Systems and the California Institute of
Technology built the MOC using spare hardware from the Mars Observer
mission. MSSS operates the camera from its facilities in San Diego,
CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA
and Denver, CO.